For example, Patent Document 1 discloses a measuring system, which measures a pulse pressure of, for example, a radial artery part using an optical sensor.
In particular, the invention according to Patent Document 1 is a blood vessel pulse wave measurement system, which performs blood vessel pulse wave measurement using an optical probe circuit provided with an optical probe. The blood vessel pulse wave measurement system includes a light emitting element and a light receiving element, where the light emitting element radiates light to a blood vessel through a skin, and the light receiving element receives, through the skin, reflected light from the blood vessel or transmitted light through the blood vessel. The blood vessel pulse wave measurement system further includes a drive circuit for driving the light emitting element based on an input drive signal; and a detection circuit for converting the light received by the light receiving element into an electrical signal, and outputting the same signal. The blood vessel pulse wave measurement system further includes measurement means, that directly and synchronously feeds back an electrical signal to the drive circuit as a drive signal to generate a self-oscillation signal from the detection circuit, and measures the self-oscillation signal as a blood vessel pulse wave signal. The blood vessel pulse wave measurement system further includes control means for controlling an operating point of at least one of the detection circuit and the drive circuit such that the self-oscillation signal substantially reaches a maximum level thereof.
FIG. 1 is a schematic view showing a configuration example of a pulse wave blood pressure meter system according to a conventional example, FIG. 1(a) is a vertical sectional view seen from a side of an MEMS pressure sensor 220, FIG. 1(b) is a bottom view seen from a contact surface in contact with a wrist, and FIG. 2 is a vertical sectional view showing a state of measurement when the MEMS pressure sensor 220 of FIG. 1 is brought into close contact with a radial artery part 7 of a wrist 8 (See, for example, Patent Document 2).
Referring to FIG. 1, the MEMS pressure sensor 220 is connected to a pulse wave blood pressure meter main unit 210 via connectors 211a and 211b by a cable to measure a blood pressure on a basis of a blood vessel pulse wave signal by a known method. In this case, as shown in FIG. 2, a blood pressure of a person under measurement can be measured by bringing the MEMS pressure sensor 220 into close contact with the radial artery part 7 of the wrist 8, and then sensing a pressure variation of a radial arterial pressure detected by the MEMS pressure sensor 220 as a pressure/voltage converted voltage signal so as to be converted into a blood pressure in a manner of making a voltage signal correspond to a standard blood pressure value measured in advance.